Within tumors, a small number of cells exist alongside the majority of more
rapidly dividing cells that constitute most of the tumor. This slowly growing subset of
cells is referred to as cancer stem cells (CSCs), and they can regenerate themselves,
allowing for the continuous growth of the tumor. CSCs were first reported in acute
myeloid leukemia by Bonnet and Dick in 1997 and have been identified in other forms
of cancer, including the brain, breast, lung, and liver tumors. These cells also show a
striking resemblance to normal stem cells, for instance, in their ability to give rise to
both the progenitor and malignant cells via asymmetric mitosis. These cells act on their
own and play a significant role in the progression of tumors, inducing metastatic foci
and bearing chemoresistance and radiotherapy resistance to standard treatments. This
resistance can be attributed to several mechanisms, including active DNA repair, noncycling state, and efflux of the drugs. They are components of the immune system that
allow them to interact with other immune cells, thus escaping any immune responses
while at the same time aiding in the recurrence of the tumors. Many crucial signaling
pathways in the body, such as Wnt/β-catenin, Notch, and Hedgehog, control neural
stem cells' actions. New therapies have been integrated against cancer aimed at cancer
stem cells, such as specific marker blocking, miRNA/LncRNA therapy, and
immunotherapy. There is also great potential in new strategies, such as
nanotechnology-based targeting of cancer stem cells to reduce the chances of tumor
recurrence. Management techniques seek to eradicate the cancer stem cell population to
mitigate the chances of recurrence and enhance treatment success.
Keywords: ALDH, Asymmetric division, Cancer heterogeneity, Cancer stem cells, Chemoresistance, Differentiation, DNA repair, Epigenetics, Epithelialmesenchymal transition, Hedgehog pathway, Immunotherapy, Markers, Metastasis, Microenvironment, Notch pathway, Proliferation, Quiescence, Selfrenewal, Tumor growth, Tumor microenvironment.
